Innate cellular antiviral responses are essential first lines of defense against viral infections, and also play crucial roles in the initiation of adaptive immunity and hence eventual virus control or clearance. However, the inappropriate activation of innate immune responses can also contribute to viral pathogenesis. Intracellular pathways that suppress or potentiate steps in innate antiviral responses therefore represent crucial components of the host-pathogen interactions that ultimately determine the outcome of viral infections. Furthermore, a detailed understanding of the cellular and molecular mechanisms underlying these pathways is important for the rationale design of novel antiviral or immunomodulatory drugs. Although our knowledge regarding innate cellular antiviral responses has progressed tremendously over the past decade, significant gaps still exist. For example, innate antiviral immune responses consist of a complex network of interactions that exhibit both cell type- and pathogen-specific differences, but the functional significance and impact of these differences on viral pathogenesis, particularly within the central nervous system, have not been well studied. We hypothesize that intrinsic maturation-dependent innate antiviral responses are key determinants in the pathogenesis of neurotropic virus infections. We propose to explore these responses in human neuronal cells using western equine encephalitis virus (WEEV), a mosquito-borne positive-strand RNA virus belonging to the Togaviridae family (genus: Alphavirus). WEEV and the closely related eastern and Venezuelan equine encephalitis viruses are category B bioterrorism agents, and cause central nervous system infections that are associated with high clinical morbidity and mortality for which there are no effective therapies. Arboviral diseases, such as those caused by neurotropic alphaviruses, have also seen both an emergence and resurgence as significant public health threats over the past several decades. The long-term objectives of this project are to elucidate the molecular mechanisms underlying the cell- autonomous recognition, activation, and effector pathways involved in the innate antiviral responses of human central nervous system neurons to arbovirus infections. The focus of this proposal is to employ targeted and global genetic and chemical genomic approaches with cultured human neuronal cells to examine the activation pathways responsible for WEEV recognition and initiation of innate antiviral responses in mature neurons. [unreadable] [unreadable] [unreadable] [unreadable]